Mechanisms defining the action potential abnormalities in simulated amyotrophic lateral sclerosis.

The present study investigates action potential abnormalities obtained in simulated cases of three progressively greater degrees of uniform axonal dysfunctions. The kinetics of the currents, defining the action potential propagation through the human motor nerve in the normal and abnormal cases, are also given and discussed. These computations use our previous multi-layered model of the myelinated motor axon, without taking into account the aqueous layers within the myelin sheath. The results show that the classical "transient" Na(+) current contributes mainly to the action potential generation in the nodal segments, as the contribution of the nodal fast and slow potassium currents to the total nodal ionic current is negligible. However, the ionic channels beneath the myelin sheath are insensitive to the short-lasting current stimuli and do not contribute to action potential generation in the internodal compartments along the fibre length. The slight changes obtained in the currents underlying the generated action potentials in the three amylotropic lateral sclerosis cases are consistent with the effect of uniform axonal dysfunction along the fibre length. Nevertheless that the uniform axonal dysfunction progressively increases in the nodal and internodal segments of each next simulated amylotropic lateral sclerosis case, the action potentials cannot be regarded as definitive indicators for the progressive degrees of this disease.

Mechanisms defining the electrotonic potential abnormalities in simulated amyotrophic lateral sclerosis.

Electrotonic potentials allow the accommodative processes to polarizing stimuli to be assessed. Electrotonic potential transients in response to applied polarizing stimuli are caused by the kinetics of underlying axonal conductances. Here, we study these transients using our multi-layered model of the human motor nerve, in three simulated cases of the motor neuron disease amyotrophic lateral sclerosis (ALS): ALS1, ALS2 and ALS3 are three consecutively greater degrees of uniform axonal dysfunctions along the human motor nerve fibre. The results show that the responses in the ALS1 case are quite similar to the normal case. In contrast, in the ALS2 and ALS3 cases, long-lasting (100 ms) subthreshold depolarizing stimuli activate the classical "transient" Na(+) channels in the nodal and in the internodal axolemma beneath the myelin sheath; this leads to action potential generation during the early parts of the electrotonic responses in all compartments along the fibre length. The results also show that the electrotonic potentials in response to long-lasting (100 ms) subthreshold hyperpolarizing stimuli in the ALS1 and ALS2 cases are quiet similar to those of the normal case. However, the current kinetics in the ALS3 case differs from the normal case after the termination of the long-lasting hyperpolarizing stimuli. In the most abnormal ALS3 case, the activation of the Na(+) channels in the nodal and in the internodal axolemma leads to repetitive action potential generation in the late parts (100-200 ms) of the hyperpolarizing electrotonic responses. The results show that the repetitive firing, due to the progressively increased nodal and internodal ion channel dysfunction, are consistent with the loss of functional potassium channels involving both the fast and the slow potassium channel types. The results confirm that the electrotonic potentials in the three simulated ALS cases are specific indicators for the motor neuron disease ALS. The mechanisms underlying the simulated ALS are also discussed.

Functional coordination of motor activity in colonic smooth muscles in rat experimental model.

Spontaneous and electrically-elicited motor activity was recorded by triple organ bath in rat segment-model preparation as display of excitation of local nerve networks and ascending or descending reflex pathways underlying contractile potency and functional coordination of colonic longitudinal and circular muscles. Spontaneous high-amplitude contractions, but not relaxations, appeared synchronously in both muscles. Electrical field stimulation applied to proximal or distal part of segments elicited both tetrodotoxin (0.1 microM)-sensitive local motor responses of the stimulated part and ascending or descending motor responses of the contralateral, nonstimulated part of the preparations. Contractions characterized the local response of longitudinal muscle. The circular muscle responded with relaxation followed by contraction. Synchronous ascending contractions and descending contraction of the longitudinal muscle and relaxation followed by contraction of the circular muscle were observed when the middle part of segments was stimulated, thus indicating that locally-induced nerve excitation propagated via intrinsic ascending or descending nerve pathways that could be synchronously coactivated by one and the same stimulus. The ascending motor responses were more pronounced and the motor responses of longitudinal muscle were expressed more than those of circular muscle suggesting an essential role of ascending reflex pathways and longitudinal muscle in the coordinated motor activity of colon.

Hormones of hypothalamic-pituitary-thyroid axis are significant regulators of synthesis and secretion of vitamin K-dependent plasma coagulation factors.

Present data about hormonal regulation of haemostasis are often contradictory and are mostly based on clinical observations. The aim of the current research is to study the effects of the hormones of hypothalamic-pituitary-thyroid (HPT) axis on plasma levels (i.e. on the synthesis and secretion) of vitamin K-dependent coagulation factors in rats. The study was carried out on 65 male Wistar rats, divided into five groups. The animals were injected subcutaneously (s.c.) once daily for three consecutive days as follows: the first group was injected with Thyrotropin releasing hormone (TRH), in a dose of 0.06 mg/kg b.w.; the second group by Thyroid stimulating hormone (TSH), with a dose of 1 MU/kg b.w., the third and the fourth group respectively with Liothyroninum (Triiodothyronin ? T3) and Levothyroxinum (Thyroxin ? T4) with a dose of 0.08 mg/kg b.w. each. The control group rats were injected with saline (the solvent of the hormones), following the same schedule and volume per kg b.w. The necessary quantity of blood was acquired by a cardiac puncture under ether narcosis, and antigen levels of plasma factors II, VII, IX and X (FII:Ag, FVII:Ag, FIX:Ag and FX:Ag) were determined by ELISA kits (Diagnostica Stago, France). TRH, TSH, T3 and T4 significantly decreased the plasma antigen levels of FII and FVII (p<0.001). TRH, T3 and TSH reduced significantly FIX:Ag level( p<0.001 for TRH and T3 and p<0.05 for TSH) while T4 did not exert significant changes ( p>0.05). FX:Ag level was also significantly reduced by TRH, T3 (p<0.001), TSH and T4 (p<0.01). Plasma levels of vitamin K-dependent coagulation factors FІІ:Ag, FVІІ:Ag, FІХ:Ag and FХ:Ag are significantly reduced under the influence of the hormones of hypothalamic-pituitary-thyroid axis which signifies their decreased synthesis and secretion. T4 does not induce substantial changes in FIX:Ag plasma level.

The myelin sheath aqueous layers improve the membrane properties of simulated chronic demyelinating neuropathies.

Recently, patients with chronic demyelinating neuropathies have demonstrated significant abnormalities in their multiple nerve excitability properties measured by a non-invasive threshold tracking technique. In order to expand our studies on the possible mechanisms underlying these abnormalities, which are not yet well understood, we investigate the contributions of the aqueous layers within the myelin sheath on multiple membrane properties of simulated fibre demyelinations. Four degrees of systematic paranodal demyelinations (two mild demyelinations termed PSD1 and PSD2, without/with aqueous layers respectively, and two severe demyelinations termed PSD3 and PSD4, with/without aqueous layers, respectively) are simulated using our previous multi-layered model of human motor nerve fibre. We studied the following parameters of myelinated axonal function: potentials (intracellular action, electrotonic-reflecting the propagating and accommodative fibre processes, respectively) and strength-duration time constants, rheobases, recovery cycles (reflecting the adaptive fibre processes). The results show that each excitability parameter is markedly potentiated when the aqueous layers within their paranodally demyelinated sheaths are taken into account. The effect of the aqueous layers is significantly higher on the propagating processes than on the accommodative and adaptive processes in the fibres. The aqueous layers restore the action potential propagation, which is initially blocked when they are not taken into account. The study provides new and important information on the mechanisms of chronic demyelinating neuropathies, such as chronic inflammatory demyelinating polyneuropathy (CIDP).

Effects of the hormones of the thyroid axis on the vitamin K-dependent plasma factors of blood coagulation (II, VII, IX, and X).

The hormonal regulation of haemostasis is a problem which has not received much attention. The data concerning the influence of hormones from the hypothalamic-pituitary-thyroid axis are scarce, contradictory and based mainly on clinical observations. The objective of the current research is to study the influence of the Thyrotropin releasing hormone (TRH), Thyroid stimulating hormone (TSH), Triiodothyronine (T3) and Thyroxin (T4) on the activity level of the vitamin K-dependent plasma factors of blood coagulation--factor II (F II), factor VII (F VII), factor IX (F IX) and factor X (F X). This study was carried out on 40 male Wistar rats. The necessary quantity of blood was obtained by cardiac puncture under ether narcosis. The indicators studied were activated partial thromboplastin time (aPTT), protothrombin time (PT), F II, F VII, F IX and F X, and were determined by means of Diagnostica Stago tests and with the help of an automatic coagulometer. The hormones studied were: TRH (0.06 mg/kg b.w.), TSH (1 MU/kg b.w.), T3 (0.08 mg/kg b.w.) T4 (0.08 mg/kg b.w.) prolonged aPTT (p<0.001) and PT (p<0.001). TRH and T3 significantly reduced the activity level of factors II, VII, IX and X; T4 only reduced the level of F II (p<0.05), and TSH did not induce significant changes in the haemocoagulation factors studied. The TRH, TSH, T3 and T4 hormones, although elements of one and the same axis, have an ambiguous effect on the vitamin K-dependent factors of blood coagulation. The results obtained show that the determined changes in the activity levels of the vitamin K-dependent plasma factors of blood coagulation are undoubtedly related to the hypocoagulation observed in the intrinsic and extrinsic pathways under the influence of the hormones of the thyroid axis.

Contributions of signal analysis to the interpretation of spirometry.

AIM: Chronic Obstructive Pulmonary Disease (COPD) is taking on catastrophic proportions. However, there is still a need for more objective and quantitative methods for its diagnosis and stratification. The present study explores the effectiveness of signal analysis methodologies as the means to increase the effectiveness of spirometry in diagnosing and stratifying COPD. METHODS: Since expiratory flow at the mouth results from converging airflows, it is possible to use signal analysis to identify changes in the characteristics of airflow along the respiratory tree. This was achieved by non-invasively identifying alterations in the frequency spectrum of the Forced Expiratory Flow (FEF) curve of 108 patients (49 men and 59 women, 12-75 yrs of age) presenting with (a) clinically and spirometrically normal respiratory profile, (b) COPD, (c) restrictive lung disease and (d) interstitial fibrosis. Fundamental to the study design was the notion that the characteristics of the expiratory output of the respiratory system are determined by the bronchial tree and the upper respiratory tract. RESULTS: A number of quantitative measures for the power spectrum of the FEF curve were identified, which permit the definition of specific rules and allow for the accurate classification of, at least, the basic types of respiratory disease. CONCLUSIONS: (a) It is for the first time that airflow resonances are identified in the sub-audible (<20 Hz) range of the power spectrum of the FEF curve. (b) COPD patients present with FEF curves which have different power spectral characteristics from those of healthy individuals (p<0.01), at frequencies lower than 3.66 Hz. (c) In COPD, in restrictive lung disease and in interstitial fibrosis, the lower resonant frequencies of the spectrum of the FEF curve predominate.

Screening study of the effects of the hypothalamic-pituitary-thyroid axis on hemostasis in rats.

The hormonal regulation of hemostasis has had little attention in research, and the existing literature data are relatively contradictory. The possible effects of the hormones of the hypothalamic-pituitary-thyroid axis on hemocoagulation and the fibrinolytic system are studied here. The study was conducted on 80 white male rats of the Wistar breed. The necessary blood quantity was obtained by cardiac puncture realized under ether narcosis. The basic parameters of the hemocoagulation and fibrinolytic activity of the plasma were determined by Diagnostica Stago tests (France), using an automatic coagulometer (Italy). The hormones employed in the study: Thyreotropin releasing hormone (0.06 mg/kg bw), Thyroid stimulating hormone (1 MU/kg bw), Triiodothyronine (0.08 mg/kg bw), and Thyroxin (0.08 mg/kg bw) applied s.c. for three consecutive days, extended the activated partial thromboplastine time (p less than 0.001), proto-thromboplastine time (p less than 0.001), thrombin time (p less than 0.001), reptilase time (p less than 0.001), and shortened the euglobin clot lysis time of (p less than 0.001). These data indicate that each of the hormones used causes significant changes in hemostasis by suppressing the coagulability by the intrinsic and extrinsic system pathways, and transformation of fibrinogen into fibrin. The shortened euglobim clot lysis time may be recognized as a manifestation of increased levels of plasma plasminogen activators. The results obtained show that hypothalamic-pituitary-thyroid hormones are significant regulators of hemostasis, since they cause an expressed hypocoagulation and increase plasma fibrinolytic activity.

Isoteoline, a putative serotonin antagonist, inhibits meta -chlorophenylpiperazine, but not 1-(2, -dimethoxy-4-iodphenyl)-2-aminopropane and 8-hydroxy-2-(di-n-propylamino)-tetraline-induced increase of serum prolactin levels.

Serotonin, in addition to dopamine and other factors, is known to participate in the control of prolactin (PRL) and gonadotropins secretion. Isoteoline (IST), a putative serotonin antagonist and dopamine agonist, was studied for its neuroendocrine effects on PRL, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). IST was given intraperitoneally to adult male rats at doses of 0.25, 1 and 4 mg kg(-1)alone and 30 min prior to the injection of three 5-HT agonists with preferential affinity for various receptor subtypes: meta -chlorophenylpiperazine (m CPP) for 5-HT2C; 1-(2, 5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) for 5-HT2A and 8-hydroxy-2-(di- n -propylamino)tetralin (8-OH-DPAT) for 5-HT1A. m CPP (2.5 mg kg(-1)), DOI (2.5 mg kg(-1)) and 8-OH-DPAT (1 mg kg(-1)) increased the serum PRL levels to a similar value, without affecting FSH and LH concentrations. IST by itself modified neither PRL nor gonadotropins serum levels. IST antagonized the m CPP-induced elevation in serum PRL, the lowest dose being the most effective. It had no effect on DOI and 8-OH-DPAT-induced increases of PRL levels and produced no significant changes in the gonadotropins levels when used as an antagonist. The results are discussed in terms of the likely involvement of serotonin vs dopamine mechanism in the effect of IST. It is concluded that the inhibition of the m CPP-induced rise of PRL levels by IST confirmed the serotonin antagonistic activity, previously demonstrated for this compound in other studies. The present results are also suggestive of possible selectivity of this antagonism of IST for the 5-HT2C vs 5-HT2A and 5-HT1A receptors, all of which are involved in the control of PRL secretion.

Serum levels of female sex hormones in left-handed and right-handed menopausal women.

The study covered 25 left-handed and 27 right-handed clinically healthy females aged between 47 and 55 years during normal menopause. It was carried out in the third year from the beginning of amenorrhoea. The levels of the follicle-stimulating hormone, luteinising hormone, proclactin, estradiol, and progesterone were determined by means of enzyme-immunological methods with IMX (Abbott, USA) and Serozyme I (Biochem Immunosystem Diagnostica, USA) apparatuses. It was established that in left-handed women the serum concentrations both of the follicle-stimulating hormone and luteinising hormone were significantly higher (P <.001), and those of prolactin, estradiol, and progesterone much lower (P <.001), as compared to the right-handed women.

Functional brain asymmetry, handedness and age characteristics of climacterium in women.

A total of 1985 women aged between 55 and 65 were distributed into two groups (145 left-handers and 1840 right-handers). They were asked to complete a questionnaire on the appearance of menopause, duration of menopausal transition and age of menopause. In left-handed women a significantly earlier appearance of premenopause was established together with a shorter menopause transition and an earlier occurrence of menopause. These results give grounds for a correlation between handedness, functional brain asymmetry, respectively and the genetically determined fading away of ovary steroidogenesis associated with the appearance and progression of the climacterium. In light of the available literature we assume that progressive reduction in ovarian function during climacterium is coupled with possible specific functioning of the hypothalamo-pituitary-gonadal axis, dependent on the type of hemispheric asymmetry.

Somatotropin and somatostatin effects on vitamin K-dependent plasma coagulation factors.

The effects of somatotropin (0.2 mg/kg body mass) and somatostatin (0.1 mg/kg body mass) on plasma coagulation factors II, VII, IX, X and some general indexes of hemocoagulation were examined. Hormones were injected subcutaneously in male Wistar rats on 3 consecutive days. Boehringer Mannheim tests and Schnitger and Gross coagulometer were used for clotting factor determination. Somatotropin caused significantly decreased activity of factors II, VII and X (P < 0.001) and IX (P < 0.05). Somatostatin alone, as well as somatotropin after somatostatin pretreatment considerably increased the activity of factors II, VII and X (P < 0.001), while factor IX was non-significantly suppressed. It is concluded that somatotropin and somatostatin are possible regulators of biosynthesis of vitamin K-dependent plasma coagulation factors. Somatotropin depresses the activity of factors II, VII, IX and X and causes hypocoagulability, while somatostatin not only prevents the inhibiting effect on factors II, VII and X, but also increases their activity and causes hypercoagulability.

Functional brain asymmetry, handedness and menarcheal age.

Functional brain asymmetry influences many functions of the organism; the neuroendocrine axis is one that has received insufficient attention. In this study we set us as the goal of studying the link between functional brain asymmetry and menarcheal age in females with left versus right manual dominance. The appearance of the first menarche was used as a natural model of functioning of the hypothalamic-pituitary-gonadal (HPG) axis. 1695 females, aged between 16 and 25 years, were interviewed by questionnaire about manual dominance and menarcheal age. 182 women were selected and divided into 2 groups: all left-handers (n = 91), and a control group of 91 right-handers. We found a significantly lower average age of menarcheal appearance in the left-handers' age of 12.09 +/- 0.16 years compared to the right-handers' age of 13.32 +/- 0.12 years (p < 0.001). The earliest menarcheal age in left-handers was 8 years and the peak of appearance at age 13 (in 30.76% of the cases). In right-handers these values were 10 and 14 years (in 40.60% of the cases), respectively. The data allow us to accept the existence of a link between functional brain asymmetry and menarche, which causes earlier activation of the HPG axis in left-handed females.

[Female sex hormones and thrombocytopoiesis]. / Zhenski polovi khormoni i trombotsitopoeza.

The influence of estradiol, estriol and progesterone was studied on basic parameters of thrombocytopoiesis and thrombocytopoietic activity of plasmas of female rats. It was established that the investigated hormones increased highly the number of thrombocytes, the percentage of 75-selenomethionine incorporated in newly formed thrombocytes and the total number of megakaryocytes. Thrombocytopoietic activity of the plasma was raised considerably only in rats, injected with estradiol, but the remaining hormones did not induce significant changes in this activity. It is accepted that estradiol, estriol and progesterone stimulate thrombocytopoiesis of female rats by various mechanisms. Estradiol increases highly the formation of specific humoral regulator of thrombocytopoiesis--throbocytopoietin. The stimulating effect of estriol and progesterone is most probably nonspecific (thrombocytopoietin-independent), as the first hormone activates proliferation of megakaryocytes greatly, but the second hormone-the differentiation of these cells.

Adrenergic dependence of the platelet aggregation in rats.

The paper examines the effect of different adrenergic agents influencing both the neuronal unit of the adrenergic transmitter system and its alpha- and beta-receptor components on the ADP-induced platelet aggregation. A considerable inhibition of the platelet aggregation is found under conditions of post-reserpine adrenergic block (16.06%, p less than 0.001) and blocking of the beta 1-adrenergic receptors with practolol, applied independently (45.06%, p less than 0.001) and prior to the treatment of the rats with dobutamine--beta 1-adrenoreceptor agonist (52.20%, p less than 0.001). The stimulation of these receptors with dobutamine accelerates the platelet aggregation by 41.04% (p less than 0.001). No changes in the platelet aggregation are found after treatment with phenoxybenzamine (nonselective alpha adrenergic blocker) and salbutamol (beta 2-adrenergic agonist). It may be concluded that the ADP-induced platelet aggregation depends to a certain extent on the functional state of the neuronal and beta-adrenoreceptor unit of the adrenergic transmitter system and possibly also on the metabolic processes connected with them.

[The effect of insulin on thrombocytopoiesis and thrombocytopoietin biosynthesis in rats]. / Vliianie insulina vurkhu trombotsitopoezata i biosintezata na trombotsitopoetin u plukhove.

The influence of insulin on the number of thrombocytes of male and female rats as well as on the percentage of 75Selenomethionine (75Se-M) incorporated, on bone marrow megakaryocytes and thrombocytopoietic activity of the plasma was studied under normal conditions. It was established that a 3-day administration of insulin induced in both go groups of rats an increase in thrombocyte number, in the percentage of incorporated 75Se-M, in bone marrow megakaryocytes as well as in their total number and in all stages from I to IV with shift to mature cellular forms (III and IV stages). The thrombocytopoietic activity of the plasma was raised as well. In conclusion it could be said that insulin stimulates strongly thrombocytopoiesis in rats as it raises considerably the biosynthesis of its specific humoral regulator thrombocytopoietin. This effect of insulin does not demonstrate sex dependence.

[Beta1- and beta2-adrenergic effects on thrombocytopoiesis in rats]. / Beta1- i beta2-adrenergicheskie vliianiia na trombotsitopoéz u krys.

The influence of beta 1- and beta 2-adrenergic agent injections to rats during 3 days, on the main parameters of thrombocytopoiesis: platelet number and per cent of build up 75seleno-methionine in newly-formed platelets of rats has been studied. It is established that beta 1-adreno-stimulation with dobutamine (DB) increases both the number of platelets and the per cent of build up isotope. Practolol (PC), a beta 1-adrenergic blocking agent, used separately, and combined application of PC + DB lowered significantly the parameters studied. Salbutamol stimulation of beta 2-adrenergic receptors induced an insignificant rise in the thrombocytopoiesis parameters. beta 1-adreno-stimulation with DB results in activation, while beta 1-adrenoblocking with PC--in suppression of thrombocytopoiesis. Pretreatment with PC prevents DB stimulating effect on thrombocytopoiesis, thus evidencing the beta 1-adrenoceptor dependence on the process.